The present invention relates generally to keyless entry systems for vehicles and, more particularly, to a protocol for a keyless entry system to provide status information to the user.
Keyless entry systems for vehicles allow users to lock or unlock the doors of a vehicle without a key. Keyless entry systems typically take the form of a pocket-sized fob with several push buttons that lock and unlock doors and perform other functions through encoded RF signals transmitted to a vehicle-installed receiver. Keyless entry systems are a great convenience to users. With a keyless entry system, a user, whose hands are burdened, can easily lock or unlock the doors of a vehicle. Keyless entry systems also allow a user to ensure that the doors are locked as the user walks away from the vehicle, and to escape harm by unlocking the doors quickly to gain entry into the vehicle when confronted by an assailant or otherwise threatened. Some keyless entry systems allow the user to activate an alarm and transmit a call for help. Further, keyless entry systems enable the user to locate a vehicle in a crowded parking lot by unlocking and relocking the doors, thereby causing the vehicle to sound its horn or flash its lights. Because of the many benefits, keyless entry systems have become standard equipment on many new vehicles.
Despite their many benefits, prior art keyless entry systems suffer from a number of limitations. One limitation is the range of the transmitter, which is limited by the requirements for miniaturization of the transmitter and the low capacity of its battery. Another limitation is the manner in which the keyless entry systems signal completion of a task. Many of today""s keyless entry systems rely on the vehicle""s horn or lights to signal completion of a task, such as locking of the doors. In certain instances, the sounding of the vehicle""s horn or flashing of the vehicle""s lights may attract unwanted attention. In other cases, the keyless entry system may not provide effective feedback, or may not provide any feedback at all. For example, a user who commands the vehicle to unlock its door often does not know until reaching the vehicle whether the task has been completed. Similarly, a user may signal the vehicle to lock its doors as the user is walking away from the vehicle. If for some reason the vehicle is unable to complete the task, an inattentive user may not be aware of the problem.
The present invention relates to a keyless entry system for a vehicle that allows two-way communication between a vehicle-mounted base unit and a portable remote unit. The portable remote unit comprises a first transceiver and a control. The transceiver in the remote unit transmits user commands to the vehicle-mounted base unit in response to actuation of the control by the user. After sending a user command to the base unit in the vehicle, the remote unit waits for an acknowledgement signal from the base unit in the vehicle. The acknowledgement signal may, for example, indicate successful receipt by the base unit of the user command or may indicate that a function or task was successfully completed. The remote unit may further include an indicator or display that informs the user that the function or task was successfully completed. In one embodiment of the invention, the acknowledgement signal may contain status information from the vehicle""s control center, which can be viewed by the user on an LCD display built into the remote unit.
In another aspect of the invention, user commands are transmitted at two distinct power levels. The remote unit initially transmits user commands at a low power level. If an acknowledgement is timely received, the process ends. However, if the acknowledgement is not timely received, the remote unit re-transmits the user command at a higher power level. Thus, the present invention conserves power by transmitting at the lower power level the majority of the time and switching to the higher power level only in those instances when the lower power level is insufficient.
In another aspect of the invention, the available user commands that can be acted upon by the base unit may be divided into classes, with each class including one or more user commands. The power level of the initial transmission of the user command from the remote unit to the base unit may be determined by the class to which the user command is assigned. For example, user commands may be divided into two classes, one class that represents commands initially transmitted at a low power level and one class that represents commands that are always transmitted at a higher power level. This concept of separating user commands into classes can be extended to three or more classes.